The December, 1914, Pacific Semaphore, a OWR&N publication on page 12, has an interesting comparison of the miles of track with "automatic electric block safety signals" installed.

Railroad

Total Miles of Track

Automatic Signaled Miles

Percent

Union Pacific

7,673

3,438

44.8%

Southern Pacific

9,134

3,719

40.7%

Northern Pacific

6,025

1,355

22.5%

C&NW

8,967

1,912

21.3%

Rock Island

7,847

1,224

15.6%

StL&SF

5,880

796

13.5%

Great Northern

6,925

881

12.7%

CM&StP

9,608

1,079

11.2%

AT&SF

10,881

751

6.9%

Iron Mountain

3,299

140

4.2%

Missouri Pacific

3,756

136

3.6%

CB&Q

9,192

251

2.7%

Submitted by Phil Beach